Modern aircraft fuselages have their shapes optimized as pressure bodies, with a circular or approximately circular cross section. The majority of the loads which occur on the outer shell as a result of the internal pressure are in the form of tangential membrane stresses. Conventional pressurized fuselages such as these may be designed for the optimum weight for the internal pressure. The pressure-tight outer skin is typically reinforced in the fuselage longitudinal direction by longitudinal frames or stringers and in the fuselage circumferential direction by annular lateral frames. The outer skin, stringers and frames form the pressure shell. If the fuselage cross-sectional shape differs significantly from this circular shape, this additionally results in bending loads in the outer shells, which must be absorbed by appropriate additional reinforcement, and this necessarily leads to an increase in weight.
Flying-wing aircraft, which are the subject matter of futuristic designs, have shells which are curved only slightly over a large cabin, which covers a large extent in the lateral direction, over large parts of the surface. Structures which are intended to absorb the correspondingly high compression and bending forces are based on the principle of conventional design with circumferential frame reinforcements. These are to have a considerably greater physical height in order to absorb the bending loads that have been mentioned. One typical feature of these conventional designs is the formation of planar frame elements in the lateral and circumferential directions.